Low temperature liquified gas storage tank

ABSTRACT

A low temperature liquified gas storage tank having an outer shell and an inner wall formed by a plurality of multi-layer panels, each panel including at least one interior liquid-tight membrane layer protected from excessive thermally induced stresses by an exterior heat shock absorbing layer of plywood or fibrous material which forms the inner wall surface of the tank. A symmetrical arrangement of the membrane layer or layers with respect to the cross-sectional center of the panel prevents warping thereof under thermally induced stress.

United States Patent 1191 Noma et al.

[ LOW TEMPERATURE LIQUIFIED GAS STORAGE TANK [75] Inventors: TetsuoNoma; Koji Hayakawa;

Osamu Nagao; Ichizo Okano; Ryuzo Teramoto; Tomomichi Kurihara; KenjiNakano; Tomiyasu Okamoto, all of Osaka, Japan [73] Assignee: HitachiShipbuilding and Engineering Company, Ltd., Osaka, Japan [22] Filed:July 6, 1972 [21] Appl. No.: 269,489

[30] Foreign Application Priority Data July 9, 1971 Japan 46-50830 521u.s.c1. 220/15, 220/9 LG, 52/417, 52/461, 161/48, 161/220, 161/250,161/270,

511 1m. 01 B65d 25/26, B65d 87/34 [58] Field 61 Search 161/220, 230,232, 250, 161/261, 268, 404; 52/404, 417, 461, 463, 481

[56] References Cited UNITED STATES PATENTS Repshcr et a1 161/220 11113,826,399 July 30,1974

2,720,478 10/1955 Hogg 161/232 2,875,117 2/1959 Potchen et a1 3,106,50010/1963 Turner .f. 3,175,940 3/1965 Talmcy 3,189,514 6/1965 Shriver etal. 161/250 Primary ExaminerGeorge F. Lesmes Assistant Examiner-WilliamR. Dixon, Jr. Attorney, Agent, or Firm-Farley, Forster & Farley 57 IABSTRACT A low temperature liquified gas storage tank having an outershell and an inner wall formed by a plurality of multi-layer panels,each panel'including at least one interior liquid-tight membrane layerprotected from excessive thermally induced stresses by an exterior heatshock absorbing layer of plywood or fibrous material which forms theinner wall surface of the tank.

A symmetrical arrangement of the membrane layer or layers with respectto the cross-sectional center of the panel prevents warping thereofunder thermally induced stress.

3 Claims, 7 Drawing Figures PAINTED- 3 3, 826.399

SHEET 1 or 4 I V F IG.4

PAIENIEDJMOIQH I 3.826.399

SHEET, 2 m= 4 I FIG.3

SUMMARY OF THE INVENTION The present invention relates to a lowtemperature liquified gas storage tank, and more particularly to such astorage tank wherein plywood panels subjected to liquid-tightnesstreatment are used as an inner tank wall applied to the inner side ofthe rigid outer shell of the tank.

In general, since plywood has a low coefficient of expansion orcontraction in connection with temperature change, it is used as a wallmaterial for low temperature liquified gas storage tanks subjected totemperature change. However, since plywood is lacking inliquidtightness, it is necessary to render it liquid-tight when it isused as an inner wall material for the tank. To this end, a lowtemperature resistant metal sheet such as of aluminum or stainlesssteel, or a synthetic resin film, has been bonded to the surface ofplywood. When such a plywood wall construction, having a metal sheet orsynthetic resin film bonded to the plywood surface, receives a lowtemperature liquid, there will be a violent shearing force acting on theinterface between the sheet or film and theplywood. This is because thethermal expansion coefficient of the metal sheet or synthetic resin filmis much greater than that of the plywood, so that a high heat shock isproduced in the metal sheet or synthetic resin film. In the case ofaluminum, for example, the thermal stress is of the order of 50-60 timesthat of plywood; Therefore, where plywood having a metal sheet orsynthetic resin film bonded to the surface thereof is used as a tankwall material for direct contact with a low temperature liquid, there isthe danger of causing the separation and cracking of the metal sheet orsynthetic resin or of causing the warping of the plywood as a result ofthe shearing force acting in the described manner. Further, since themetal sheet or synthetic resin film is intended for providingliquid-tightness, not for supporting the pressure of low temperatureliquid, the thickness, thereof may be as thin as the order of 0.3 0.lmm. Therefore, when plywood having such a thin metal sheet or syntheticresin film exposed on the plywood surface is used to form a tank wall,there is a disadvantage that it is liable to be damaged by contact withother objects during the tank wall forming operation.

For the above reasons, it is seen that a low temperature liquified g'asstoringtank constructed of plywood having a metal sheet or syntheticresin film bonded to the surface thereof has drawbacks due to thermalfactors and mechanical damage.

The low temperature liquified gas storage tank of the present inventionovercomes the problems described above, and comprises an outer tankshell, a plurality of panels mounted inside of and spaced from the outershell to form an inner wall of the tank, and a heat insulator interposedbetween the outer shell and inner wall; wherein said panels are each ofmulti-layer construction and include at least one interior liquid-tightmembrane layer and an exterior heat shock absorbing layer forming theinner wall surface of the tank.

Other features and advantages of the invention will appear from thedescription to follow of the embodiments thereof shown in theaccompanying drawings.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematicsectional elevation ofa tank installed on the ground; I

FIG. 2 is a schematic sectional elevation of a tank installed in a ship;FIG. 3 is an enlarged perspective view in transverse section through thewall of the tank showing one of the embodiments of the invention;

FIG. 4 is an enlarged sectional view through a portion of the inner wallof a tank showinganother embodiment of the invention;

FIGS. 5 and 6 are perspective views each showing other forms ofliquid-tight wall panel constructions of the invention; and,

FIG. 7 is a graph explanatory of heat shock absorbing effects. i a

DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIGS. 1 and2, thistype of tank is formed usually of a tank body A and a secondaryprotective wall B for prevention of the outflow of a low temperatureliquid in the event of damage to the tank body. In the followingembodiment, only the secondary protective wall will be described, butthe secondary protective wall may, of course, be employed as a liquidstorage tank. Further, in one case the tank is built on the ground asshown in FIG. 1 and in another case it is built in a ship as shown inFIG. 2.

The inner wall of the tank is constructed by connecting a number ofrectangular liquid-tight panels'end-toend.

'Multi-layer liquid-tight panels 1 shown'in FIG. 3'are each constructedby bonding liquid-tight membrane layers 4a and 4b of low temperatureresistant metal to both sides of a plywood core 3, consisting of aplurality of veneers 2, and then bonding veneers 5a and 5b to thesurfaces of said liquid-tight membranes 4a and 4b to serve as heat shockabsorbing layers. The veneer 5a of the panel 1 which will be in directcontact with low temperature liquid is cutaway in advance overapredetermined width from'the edge thereof to form a bandlike exposedmembrane portion 6. Connector joists 8 are disposed'in a lattice-likepattern within the interior of an outer wall 7 of ordinary steel plateso as to be in conformity with the size of the liquid-tight panels 1 andare secured to said outer wall through stay plates 9. The adjacent edgeportions 10 of such liquid-tight panels 1 are placed on one of thejoists 8, and 'a connector patch member 12 is bonded to the outer sideof said adjacent edge portions 10 over the band-like exposedmembranesurfaces 6 by means of an adhesive 11. The width of the patch member 12is such that some areas of the bandlike exposed membrane portions 6 areleft uncovered on both sides of the patch member 12. Fasteners such asnails 13 are driven through the patch member 12 into the wooden joist 8through both panels 1, thereby securing the adjacent end portions 10 tothe joist 8. Fi-

nally, a coating layer 14 of low temperature resistant 9, the outer wall7 and the, low temperature resistant liquid-tight panels 1 throughopenings in said latticelike enclosure and allowing the material'to foamin said space; or, by filling the lattice-like enclosure with apreformed heat insulator before the low temperature resis tantpanel 1 issecured in position.

As a result of the above construction, there is no exposed portion ofthe liquid-tight membranes 4a; direct contact of a low temperatureliquified gas contained in thetank with the liquid-tight membranes 4a ispositivelyprevented by the veneers 5a and the coating layers l4; and,the liquid-tight membranes 4a of adjacent panels 1 are liquid-tightlyinterconnected by the coating layers 14, so that there is no possibilitythat any liquid; which has permeated the veneers So will leak throughthe junctions of the panels.

Further, when the liquid-tight panel 1 shown in the above embodiment isused, it is,-of course, possible to prevent the separating andcrackingof the membranes by absorbing in the exterior layer 5a the heatshock caused by direct contact between the surface of the iunerlwall ofthe tank and the low temperature liquid, and since the membranes 4a and4b of low temperature resistant metal are symmetrically arranged withrespect to the center of the panel and expand and contract approximatelyequally, such expansion and contraction of the membranes .4a'and 4b willnot result in warpingthe panel 1. Thus, the entire liquid-tight panelcan ideally. expand and contract.

- In'FIG. 3, single ply veneers Sa'and 5b are bonded to the surfaces ofthe liquid-tight membranes 4a and 4b, but a laminate formed by aplurality of veneers may be bonded thereto as a heat shock absorbingmaterial.

I As forthe method of interposing a membrane of low temperatureresistant metal between layers of the panel, a method may be employedwherein hot pressing is carried out with a resin-impregnated paper sheetinterposed between said membrane and the layer on each sidelof themembrane.

FIG. 4 shows 'a different embodiment of the invention; A liquid-tightpanel used in this embodiment consists of two plywood layers 21a and 21bof approximately the same thickness with a liquid-tight mem brane 22 oflow temperature resistant metal interposed therebetween. Ifsuch a panel20 is applied to the embodiment shown in FIG. 3, since the thickness ofthe plywood 21a working as a heat shock absorbing material with respectto the liquid-tight membrane amounts to about half the thickness of thepanel 20, a bandwise cutting away of the plywood 21a for placing aconnector patch member on the cut away area would result in the adjacentedge portions of the panels being too thin, thus presenting a problem ofstrength. Therefore, as shown in FIG. 4, a connector patch member 23 isbonded directly to the surfaces of adjacent panels20 by an adhesive, andthe adjacent edge portions 25 of the panels 20 are secured to aconnector joist 26 by fasteners24. On both sides of said patch member23, grooves 27 reaching the liquid-tight membranes 22 are provided inthe plywood 21a parallel to the patch member 23. Each groove 27 isfilled with a low temperature resistant adhesive 28 so as to be incontact with the liquid-tight' membrane 22, and a coating layer 29 oflow temperature resistant adhesive covering the patch member'23 isunited with said low temperature resistant adhesive 28, therebyinterconnecting the panels 20 in a liquid-tight manner without involvingany problem of strength.

Further, as in the embodiment shown in FIG. 4, by placing theliquid-tight membrane centrally of the panel, it is possible to avoidheat shock caused by direct contact with low'temperature liquid and,moreover, in spite of the use of a single membrane there is nopossibility that warping of the plywood will take place due to theexpansion and contraction of saidmembrane.

FIGS. 5 and 6 show other embodiments of the liquidtight panels ofthepresent invention. in FIG. 5, a liquidtight panel 30 is constructedby bonding liquid-tight membranes 33a and 33b of low temperatureresistant metal or synthetic resin to both sides of plywood 32consisting of a plurality of layers of veneers 31 and then bonding asoft fibrous material 34 of suitable thickness to the outer side of onemembrane 33a to form a heat shock absorbing layer. The fibrous materialmay be a wood fiber plate, a thick fabric, a laminated thin fabric, arug or the like. r p Although the low temperature liquid permeates thefibrous material 34 when the fibrous material 34 forms the inner surfaceof the tank, permeation beyond the same is prevented by the liquid-tightmembrane 33a. Therefore, heat shock caused by direct contact between theliquid-tight membrane 33a and the lowtemperature liquid can be avoidedby the fibrous material 34, so that there is no possibility of themembrane 33a coming off or cracking. Further, since the liquid-tightmembranes 33a and 33b are positioned on both sides of the plywood 32 andexpand and contract approximately equally, there will be no possibilitythat the plywood will warp as a result of the expansion and'contractionof the membranes 33a and 33b.

A liquid-tight panel 40 shown in FIG. 6 is constructed by interposingtwo or more layers of low temperature resistant resin-impregnated papersheets 43 between layers 41 and 42 of plywood and subjecting theassembly to a hot press process. In this liquid-tight panel, the thermalstresses produced in the liquid-tight membranes are very small ascompared with the case of using a low temperature resistant metal sheet,so that the plywood vvillnot warp. Further, the low temperatureresistant resin-impregnated paper sheets 43 are easy to bring into closecontact with'the plywood layers, so that the production of theliquid-tight panel is facilitated.

As described above, according to the invention, an interior liquid-tightmembrane layer within an exterior layer of plywood or a fibrous materialmakes it possible to mitigate the heat shock 'due to direct contact ofthe inner wall surface of the tank with low temperature liquid. Forexample, in the case where a membrane exists within plywood and there isa temperature difference of C between the membrane and the plywood,changes in temperature which take place in the interior of the-plywoodare as shown in FIG. 7. From this it is seen that in the case of atemperature difference of about 60C,-if there is a plywood layer (heatshock absorbing layer) which is more than 3mm thick, this makes itpossible to greatly mitigate heat shock. Therefore, there will be noseparation or cracking of the membrane, which, in turn, contributes somuch to the prevention of warping of the plywood. Further, since suchmembrane is internally provided, there is no possibility thatthemembrane will be damaged at the time of constructing the tank wall.Therefore, the handling is easy and the construction of the tank wallcan be carried out more easily and rapidly than in the case of the priorart.

We claim:

1. A low temperature liquified gas storage tank having an outer wall ofsteel, an inner wall of plywood panels spaced from the outer wall, and asolid heat insulat- I wall surface of the tank; and,

fastening means for securing adjacent edge portions of said plywoodpanels to the joists, said fastening means including a patch coveringsaid adjacent edge portions and an adhesive covering the patch andcovering portions of the panels adjacent to the patch.'

2. A low temperature liquified gas storage tank according to claim 1wherein each of said plywood panels includes two of said liquid-tightmembrane layers symetrically arranged cross-sectionally of the panel.

3. A low temperature liquifled gas storage tank according to claim 1wherein each of said plywood panels includes a heat shock absorbinglayer forming the surface of the panel opposed to said inner wallsurface of the tank.

1. A low temperature liquified gas storage tank having an outer wall ofsteel, an inner wall of plywood panels spaced from the outer wall, and asolid heat insulating layer interposed in the space between the outerand inner walls, wherein wooden joists attached to the inner surface ofthe outer wall define the depth of the space for said insulating layer;said plywood panels each include at least one interior liquidtightmembrane layer composed of thin sheet metal or of resinimpregnatedpaper, and a wood fiber or fabric heat shock absorbing layer, said heatshock absorbing layer forming the inner wall surface of the tank; and,fastening means for securing adjacent edge portions of said plywOodpanels to the joists, said fastening means including a patch coveringsaid adjacent edge portions and an adhesive covering the patch andcovering portions of the panels adjacent to the patch.
 2. A lowtemperature liquified gas storage tank according to claim 1 wherein eachof said plywood panels includes two of said liquid-tight membrane layerssymetrically arranged cross-sectionally of the panel.
 3. A lowtemperature liquified gas storage tank according to claim 1 wherein eachof said plywood panels includes a heat shock absorbing layer forming thesurface of the panel opposed to said inner wall surface of the tank.